As a background art in this technical field, for example, Patent Document 1 has been known. Patent Document 1 describes a technology including redundant angular velocity sensors. More specifically, the paragraph [0011] of Patent Document 1 describes that a plurality of angular velocity sensors having a fault diagnosis circuit which outputs fault signals at the time of faults, discrimination means which determines presence or absence of faults of the angular velocity sensors and a faulty angular velocity sensor and step-voltage output means which changes fault signals in a stepwise manner based on output signals from the discrimination means are provided, and output signals of the angular velocity sensors other than the faulty angular velocity sensor are transmitted to an external computer.
Further, Patent Document 2 and Patent Document 3 are also known as background arts in this technical field. Patent Documents 2 and 3 describe the technologies of sharing a detecting circuit among a plurality of axes. More specifically, the following contents are described. That is, the paragraph [0025] of Patent Document 2 which explains FIG. 1 thereof describes that a diagnosis voltage control unit 167 forcibly displaces an oscillator 128 in an X axis direction and an oscillator 129 in a Y axis direction and applies a voltage to electrodes 131 and 133 in order to diagnose whether an acceleration sensor is operating properly. Further, FIG. 11 of Patent Document 3 describes that a carrier wave application circuit 18 applies carrier waves to variable capacitors 21a, 21b, 22a and 22b with having orthogonal sensitivities (detection axes).